I've done it up to a week after - the milk came back to the ewe. It was an extraordinary year and I wouldn't normally attempt it after more than about 48 hours, but that year we did several at 3, 4 and 5 days and most of them worked. These were moorland Swales.
I have only ever tried to foster a single on, no matter how many she lambed.
I think you'd do it no bother in an adpoter, or quite probably get it to work in a small pen - generally when they are bereaved, they are desperate to have a lamb to raise and will accept a foster without too much argument. Less so when it's their first time lambing, mind.